Monday, March 26, 2018

Why "Loads" Matter

A night that started out with fun, partying, and dancing, ended in tragedy. On July 17, 1981, 100 people were killed, and nearly 200 injured, when an elevated walkway collapsed at the Hyatt Regency in Kansas City.

The 40-story Hyatt Regency had opened its doors only one year before this incident. The defining features of the structure were the elevated walkways that were suspended from the ceiling.  Each walkway was about 40 yards long, and weighed 63,934 pounds. These walkways were configured in such a manner that the second and fourth level walkways were in line vertically.



The original design for these walkways was that they would be suspended from the ceiling with continuous threaded rods and secured with nuts. Contractors and the manufacturer had concerns regarding the installation and workload required to install and secure four-story long threaded rods, and then rotate nuts two stories into place. So, a decision was made to hang the fourth floor walkway from the ceiling, and suspend the second floor walkway from the fourth with a different set of rods.  This design change was approved without a detailed review, or revised calculations.

This configuration doubled the load on the main supporting beams (from which supported the fourth floor walkway).  The added load caused the welded seam beams to fail and allowed the nuts to pull through. This caused the fourth floor walkway to “pancake” onto the second floor walkway beneath.



The full investigative report is available here, from NIST.  

Primary contributing factors identified in the cause of this collapse, include:
  • Design changes
  • Poor communication
  • Improper testing of the new design
  • Poor, or no, load calculations of the new design
  • General negligence